International drug traffickers have long used people as mules to smuggle their products overseas but a massive bust in Colombia suggests they are now using the same method to bring their dirty cash home.

On Thursday Colombian authorities at Bogotá’s international airport arrested 27 people accused of swallowing wads of cash and bringing them into the South American nation from Mexico. The money, sent by Mexican drug cartels, was intended to pay Colombian gangs for cocaine.

Authorities said that mules often swallowed up to 120 pellets of cash, with five $100 bills in each latex capsule. A typical ingestion would conceal and move $40,000 a person, though investigators said they previously caught someone with $75,000 in their system.

US Immigration and Customs Enforcement (Ice) assisted with the operation that brought down Thursday’s smuggling ring.

The mules, usually paid around $1,500 for their services, would have been taken to a hotel while they waited to pass the cash. Officials said that cartels often employ young unemployed men and women to ferry their cash.

The grim practice is more commonly associated with cocaine, which can result in death for the mule if the capsule tears. Some mules are unwittingly sent with the intention of getting caught, providing cover for other passengers by distracting authorities.

Thursday’s bust highlighted the links between Mexican and Colombian drug gangs which have long shared mutual business interests. Colombian criminal groups, including leftwing rebel groups such as the National Liberation Army and dissidents from the now-demobilised Revolutionary Armed Forces of Colombia (Farc), control cocaine production while Mexican cartels handle the drug’s onward passage to the US.

Colombia is the world’s top cocaine producer, producing a record estimated 1,379 tonnes last year – up 31% on 2016 - according to a recent UN report.